added GPU non local means brute force filter + tests

added posibility to specify device on which tests will be executed

minor refactoring of gpu tests

added additional tests for gpu filters
fixed gpu features2D tests

fixed some bugs in gpu module

refactored tests for them

fixed several warnings

wrote more complicated tests for them
implemented own version of warpAffine and warpPerspective for different border interpolation types
refactored some gpu tests

update gpu tests